Research On Full Speed Range Control Strategy Of Electrical Locomotive Traction Motor

The control of locomotive traction motor is one of the key techonology and its performeance is of great important to the running of electrical locomotive. This dissertation is based on the research and development of domestic high power electrical lomotive and aims to solve some key problems of the motor control in the traction driving system.First, the relationship between incorrect rotor time constant, load and the rotor flux angle error is analyzed, and the influence of angle error to performance of vector control is detailed researched in this article. A q-axis rotor flux based correction strategy of field orientation in real-time is used based on the compareration of different methods. Simulation and experimental results proved the validity of the strategy.Second, the output voltage of inverter is constant and can’t be adjusted any more under square wave, which make the traditional vector control can’t be used. In this article, a modified vector control based on open loop current control is proposed and a max-torque control method based on modified voltage controller is used in order to get maximum torque output in the whole speed range.Third, based on the influence research of incorrect field orientation on current error between command and actual value, a corrention strategy for field orientation under square wave which is based on the q-axis current error is proposed, thus the accurate torque control can be get even in the one pulse mode.Fourth, two modulation method:central60°modulation and SHEPWM under low carrier wave ratio are learned. Most attentation is paid on the voltage harmonics and the current harmonics, resulting torque pulsation in induction machine analization. The affects of different initial swithing angle to the harmonic amplitude of the SHEPWM is also researched, and a conclusion is given. The transition between different modulation methods is an important aspent in the multi-mode modulation strategy, a transition strategy that three phases can swith at the same time is proposed.Fifth, a sectional vector control strategy within the whole speed range is proposed based on the speed of electrical locomotive, and the proposed control and modulation strategy are used in the domestic electrical locomotive. Besides, a constant DC bus voltage control strategy when passing the neutral section is proposed which can achieve uninterrupted power supply for auxiliary system of electric locomotive. A quasi-constant speed control ot locomotive using a proportional controller based on the speed error is used, which can guarantee that the speed error can’t exceed2.5km/h. The expremental results of the locomotive using the control strategy and modulation strategy is presented and it showed that the performance of the locomotive is very good and achieves the designed goal of the traction driving system.